Review-Understanding the Thermal Runaway Behavior of Li-Ion Batteries through Experimental Techniques

Heavy duty Li-ion batteries in the electric vehicles suffer from serious safety issues due to their operation in abuse conditions. The worst consequence of these conditions is the thermal runaway, which causes a dramatic rise in temperature and pressure leading to a catastrophic failure of the battery. Therefore, precise determination of thermal runaway behavior of the battery under different abusive scenarios holds critical importance. This paper reviews the understanding of the thermal runaway behavior of Li-ion batteries through experimental routes. The impact of initial conditions (SoC, overcharge and ageing) and design (geometry, material and capacity) of the battery on the severity of thermal runaway is extensively discussed. It is observed that the thermal runaway becomes more severe in high SoC, overcharged and aged batteries, and the mechanism of thermal runaway primarily depends on the battery design. The quantification of the fire-induced hazards is presented in terms of the heat release rate. Further, we observe that the electrical and mechanical abuse conditions induce an internal short circuit in the battery due to a component collapse. We also briefly review the prevention techniques of thermal runaway which include detection modelling, heat dissipation strategies and the use of the non-flammable electrolytes. (c) 2019 The Electrochemical Society.